The present invention relates to electronic testing apparatus, and more particularly to an integrated test socket apparatus that is configured to test sound transducers, and a method of using the same.
Consumer electronics devices are continually getting smaller and, with advances in technology, are gaining ever increasing performance and functionality. This is clearly evident in the technology used in consumer electronic products such as smart phones, laptop computers, tablet devices, wearable devices, as well as other electronic devices. Requirements of the smart phone industry, for example, are driving components to become smaller with higher functionality and reduced cost. Smart phones now require multiple microphones for noise cancelling, or accelerometers to allow inertial navigation, while maintaining or reducing the small form factor and aiming at a similar total cost to previous generation phones. This has encouraged the emergence of miniature sound transducers. With respect to speech applications, initially electric condenser or moving coil elements were used in microphones to capture speech, but more recently micro-electrical-mechanical (MEMS) sound transducers have been introduced.
Traditional MEMS sound transducers are capacitive transducers, which typically comprise one or more membranes with electrodes for read-out. Relative movement of these electrodes modulates the capacitance between them, which then has to be detected by associated electronic circuitry such as sensitive electronic amplifiers.
MEMS sound transducers typically are manufactured in wafer form and then separated into individual die after manufacturing is completed. Each MEMS die is then assembled into a protective package structure, which typically comprises a substrate that the MEMS die is attached to. The substrate may also include an associated electronic analog amplifier and an additional analog-to-digital converter in the case of digital microphones. Conductive structures such as wire bonds are used to connect the MEMS dies to the electronic circuitry on the substrate, which facilitates passing of electrical signals out of the MEMS structure. A molded plastic housing or a metal can lid or an encapsulating layer is then attached or formed to protect the MEMS die, conductive wires and associated circuitry from damage caused by handling the device. A port or passage in the housing or molded layer allows the MEMS sound transducer to measure sound waves by changes in air pressure, which is then converted to an electrical signal.
After assembly, the MEMS sound transducers are then tested by attaching them to test boards using test sockets. In the past, the test boards were then placed inside a sound chamber apparatus, which provided the sound stimulus to test the devices to make sure they met predetermined electrical specifications. Several problems existed with this prior approach including the high cost of the sound chambers. The sound chambers were custom built and hand assembled, which caused large unit-to-unit variation. Also, the sound chambers tended to be bulky and their large size increased the possibility for the existence of multi-path signals, which further limited the ability to provide uniform sound intensities within the sound chamber and thus, limited the number of devices that could be tested at one time. Additionally, the bulky sound chambers typically did not integrate well into standard robotic device handlers and therefore required custom handler design to accommodate them. Finally, Outsourced Assembly and Test (OSAT) companies typically preferred to purchase equipment that was generic and that could be reused when a device comes to its end of life rather than application specific equipment tailored to one device type, which was typically the case with previous sound chamber designs.
Accordingly, it is desirable to have an apparatus and method that improves the testing of sound transducers such as MEMS microphones and provides flexibility to the OSAT. Further, it is desirable that such apparatus be cost effective, facilitate the testing of multiple devices, and measure the sound stimulus in real time while using existing device handling equipment.
For simplicity and clarity of the illustration, elements in the figures are not necessarily drawn to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description.